As local fishermen tell it, the deep blue “Dragon Hole” in the
Paracel Islands, called the “eye” of the South China Sea, is where the
Monkey King in “Journey to the West” acquired his famous golden cudgel.
The
mythical tale was published in the 16th century and is among the four
great classical novels of Chinese literature.

Plunging 300.89 meters in the sea, it's named "Sansha Yongle Dragon Hole",surpassing the current record of 202 meters, state-run Xinhua news agency reported

Last week, the Dragon Hole
earned a new claim to fame.
After nearly a year of exploration,
Chinese researchers have determined that the underwater sinkhole is
likely the world’s deepest, reaching about 987 feet below the surface
and surpassing the previous record holder, Dean’s Blue Hole near the
Bahamas, by more than 300 feet, Xinhua News Agency reported.

inside the Nine-dash line...

The hole was found near the Paracel islans called as Xisha Islands by China.The islands are claimed by China, Vietnam and Taiwan.

China has continued to assert its claim over all but most of the South China Sea even after this month's verdict by the international tribunal appointed by the Permanent Court of Arbitration which has struck down its claims of nine-dash line based on historic rights.

Blue
holes are named as such for their rich, dark blue coloring, a stark
contrast to the otherwise aqua waters that surround them.
Best described
as underwater caves,
these striking and beautiful formations open up with underwater
entrances and extend below sea level, mirroring the appearance of a
sinkhole.

Researchers with the Sansha Ship Course Research Institute for Coral
Protection began exploring Dragon Hole, known as Longdong, in August
2015 and completed the project last month, Xinhua reported.
It measures
about 426 feet wide and is almost deep enough to hold the entire Eiffel
Tower.

The research team used a Video Ray Pro 4 underwater robot to explore the sinkhole, reported CCTV News,
where they discovered more than 20 species of fish and marine life near
the surface of the vertical cave.
Researchers told the television
station that after about 330 feet, the water is oxygen free and likely
unable to support life.
On July 24, CCTV reported that the Sansha city government had officially named the sinkhole the Sansha Yongle Blue Hole.
The city said it has drafted plans to continue to protect and study the blue hole.
“We will strive to protect the natural legacy left by the Earth,” Xu Zhifei, vice mayor of Sansha City, told Xinhua.

Researchers investigate the newly named Sansha Yongle Blue Hole

Across the globe, blue holes have been the source of magnificent discovery.
Last year, the Guardian reported
that a study conducted by scientists from Rice University and Louisiana
State University found that sediment samples from the ancient Great
Blue Hole in Belize confirmed the theory that “drought and climate
conditions pushed the Mayans from a regional power to a smattering of
rival survivors and finally a virtually lost civilization.”
Divers flock to the Great Blue Hole, surrounded by shallow, lagoon waters and a coral island. According to Atlas Obscura,
this underwater cave was made famous by one particular diver, explorer
Jacques Cousteau, who in 1971 declared the site one of the top 10 best
places for diving in the world.
Cousteau sailed on his ship, Calypso, to
investigate the hole’s depths and discovered huge stalactites and
stalagmites below the surface, Atlas Obscura reported.
Cousteau also
confirmed that the sinkhole had formed when a limestone cave formation
collapsed after the glacial period.

Dean’s Blue Hole, located near Long Island in the Bahamas, was
previously considered the world’s deepest underwater sinkhole.
Also a
top location for divers, Dean’s Blue Hole has a diameter of about 82 to
115 feet on the surface, reports Atlas Obscura,
but widens to about 330 feet as it deepens.
According to the
publication, water there is very clear with visibility as far as 115
feet down.

Maximum depths in other blue holes scattered throughout the Bahamas
and other parts of the world hover around 360 feet, but Dean’s Blue Hole
extends far beyond at 663 feet deep.
The newly discovered Dragon Hole is even more exceptional, reaching depths of almost 1,000 feet.